NAME

     zpool-scrub — begin or resume scrub of ZFS storage pools

SYNOPSIS

     zpool scrub [-s|-p] [-w] pool…

DESCRIPTION

     Begins a scrub or resumes a paused scrub.  The scrub examines all data in the specified pools to verify
     that it checksums correctly.  For replicated (mirror, raidz, or draid) devices, ZFS automatically repairs
     any damage discovered during the scrub.  The zpool status command reports the progress of the scrub and
     summarizes the results of the scrub upon completion.

     Scrubbing and resilvering are very similar operations.  The difference is that resilvering only examines
     data that ZFS knows to be out of date (for example, when attaching a new device to a mirror or replacing an
     existing device), whereas scrubbing examines all data to discover silent errors due to hardware faults or
     disk failure.

     Because scrubbing and resilvering are I/O-intensive operations, ZFS only allows one at a time.

     A scrub is split into two parts: metadata scanning and block scrubbing.  The metadata scanning sorts blocks
     into large sequential ranges which can then be read much more efficiently from disk when issuing the scrub
     I/O.

     If a scrub is paused, the zpool scrub resumes it.  If a resilver is in progress, ZFS does not allow a scrub
     to be started until the resilver completes.

     Note that, due to changes in pool data on a live system, it is possible for scrubs to progress slightly
     beyond 100% completion.  During this period, no completion time estimate will be provided.

OPTIONS

     -s  Stop scrubbing.

     -p  Pause scrubbing.  Scrub pause state and progress are periodically synced to disk.  If the system is
         restarted or pool is exported during a paused scrub, even after import, scrub will remain paused until
         it is resumed.  Once resumed the scrub will pick up from the place where it was last checkpointed to
         disk.  To resume a paused scrub issue zpool scrub again.

     -w  Wait until scrub has completed before returning.

EXAMPLES

     Example 1: Status of pool with ongoing scrub:
           Output:
                 # zpool status
                   ...
                   scan: scrub in progress since Sun Jul 25 16:07:49 2021
                         403M scanned at 100M/s, 68.4M issued at 10.0M/s, 405M total
                         0B repaired, 16.91% done, 00:00:04 to go
                   ...
           Where:

                 -   Metadata which references 403M of file data has been scanned at 100M/s, and 68.4M of that
                     file data has been scrubbed sequentially at 10.0M/s.

PERIODIC SCRUB

     On machines using systemd, scrub timers can be enabled on per-pool basis.  weekly and monthly timer units
     are provided.

             systemctl enable zfs-scrub-weekly@rpool.timer --now

             systemctl enable zfs-scrub-monthly@otherpool.timer --now

SEE ALSO

     systemd.timer(5), zpool-iostat(8), zpool-resilver(8), zpool-status(8)